CNC pen / sharpie holder for plotter

Use your CNC router as a plotter!
This was inspired by TadasM https://www.thingiverse.com/thing:1847711
However I wanted to make it easy and cleanly printable without any supports, imperial instead of metric and working with sharpie so I created my very own version from scratch in Fusion 3D. I love the concept where the spring is incorporated in the design! (And it works!)
This uses 1/4" 4" screw from home depot that has only small thread length at the end - just cut out the thread and you have a perfect 1/4" shaft of 3 1/4 length for this project.
All other screws are 8-32 - the class 2b threads are perfectly realized in the stl, no need to retap.

All dimensions are very precisely set in the file; the top collar fits very very tightly and stays even without the screw and the bottom collars slide freely but without any play on the shaft. The screw holes all have 8-32 thread realized and manually adjusted for exact fit.
The hole fits the standard sharpie and the double sided sha